Polysaccharides with oxime or amine functions which are used for water treatment and sludge conditioning

ABSTRACT

The invention relates to a particular polymer which is derived from a copolymer polysaccharide formed by a main chain comprising similar or different anhydrohexose units and branches including at least one neutral or anionic anhydropentose and/or anhydrohexose unit. Moreover, the invention relates to the use of said polymer in the treatment of aqueous media, in particular the treatment of aqueous effluents containing heavy metals, the treatment of waste water, drinking water and for sludge conditioning. Said derivative polymer comprises one or more units bearing an oxime function at least at position C2.

[0001] The present invention relates to the use, for treating aqueousmedia, in particular for treating aqueous effluents containing heavymetals, for treating waste water or drinking water, or for conditioningsludges, of a polymer which is derived from a polysaccharide whichcarries lateral sugars and carries at least an oxime function in the C2position or of a polymer which comprises at least an amine function inthe C2 position, with this polymer being obtained from the precedingpolymer.

[0002] One the one hand, the polysaccharides which are encounteredcomprise for the most part chains of various sugars which are linked toeach other and which, in addition to the primary alcohol functions or,possibly, aldehyde or ketone functions, mainly exhibit secondary alcoholfunctions.

[0003] One of the rare polysaccharides to differ in this regard ischitosan. This polysaccharide is obtained by deacetylating chitin, whichis a structural polymer in the exoskeletons of arthropods, theendoskeletons of cephalopods or else the cell walls of some fungi oralgae. It consists of repeated D-glucosamine units which are linkedβ-(1->4), containing up to 40% N-acetylglucosamine residues. In the caseof the lowest contents of acetylated residues, the intrinsic pK of theamine function in protonated form is very low (approximately 6.5) ascompared with the other polyamines; chitosan possesses, in particular,metal-chelating capacities which are not possessed by the otherpolysaccharides.

[0004] However, one of the major drawbacks of chitosan is the cost ofthis product.

[0005] The high cost of chitosan is due to the fact that chitin, whichis the product from which it is derived, originates from the carapacesof marine animals such as crabs, krill, the squid endoskeleton, etc.Steps of preliminary treatment therefore have to be carried out in orderto extract the chitin. In addition, the volumes of chitin which areavailable are limited simply due to the origin of this product.

[0006] A further constraint is that of the chemical treatments which arerequired for obtaining the chitosan. Thus, the deacetylation is mostfrequently effected using 40-50% sodium hydroxide solution. Furthermore,these chemical treatments can prove to be polluting and therefore makeit necessary to implement processes for treating the effluents, therebyincreasing still further the cost of the final product.

[0007] On the other hand, it is known to use various agents during thetreatment of (urban or industrial) waste water and during the treatmentof, in particular when obtaining, drinking water. Ferrous or ferricchloride, ferrous or ferric sulfate, ferric chlorosulfate and aluminumchloride may thus be mentioned. It is also possible to use aluminumpolychlorides or aluminum polychlorosulfates.

[0008] In addition, the water used for washing (or purifying) the smokefrom factories for incinerating household refuse or industrial wasteconstitutes a medium containing heavy metals, which heavy metals thenhave to be removed.

[0009] Finally, the treatment of urban or industrial sewage, inparticular by the biological route, leads to the formation of sludges.These sludges are generally subjected to a mechanical dehydrationprocedure (in particular filtration (for example filter press or bandfilter) or centrifugation) before being transported to a dumping site ora site for agricultural spreading or incineration. The sludges to betreated mainly consist of water in which biomass is dispersed. Thetreatments are therefore directed toward concentrating the dry matter tothe greatest possible degree and removing water.

[0010] The aim of the present invention is therefore to propose usingnovel modified polysaccharides, which advantageously do not exhibit theabovementioned drawbacks of chitosan, for treating aqueous media, inparticular aqueous, for example industrial, effluents, in particularthose loaded with heavy metals, waste water or drinking water, or forconditioning sludges.

[0011] These aims, and others, are achieved by the present invention,which relates, in the first place, to the case, for the treatment ofaqueous media or for sludge conditioning, of at least one polymer whichis derived from a copolymeric polysaccharide which is formed from a mainchain which comprises similar or different anhydrohexose units andbranches which comprise at least one neutral or anionic anhydropentoseand/or anhydrohexose unit, with said derived polymer comprising one ormore units which carry(ies) an oxime function at least in the C2position and being capable of being obtained by implementing thefollowing steps:

[0012] a) bringing a polysaccharide into contact with an aqueoussolution which comprises at least one oxidizing agent which enables atleast the hydroxyl radical carried by the C2 carbon of one or more unitsto be oxidized to a ketone function;

[0013] b) bringing the resulting polymer into contact withhydroxylamine, or a derivative, in order to transform the ketonefunction into an oxime function.

[0014] In the second place, the present invention relates to the use,for the treatment of aqueous media or for sludge conditioning, of atleast one polymer which is derived from a copolymeric polysaccharidewhich is formed from a main chain which comprises similar or differentanhydrohexose units and branches which comprise at least one neutral oranionic anhydropentose and/or anhydrohexose unit, with said polymercomprising one or more units which carry(ies) an amine function at leastin the C2 position and being capable of being obtained by implementing astep c) which consists in bringing the polymer possessing one or moreunits carrying an oxime function at least in the C2 position intocontact with an agent which reduces the oxime function.

[0015] It has been observed that the novel polymers which are used inthe invention are preferentially effective in treating waste water,which may possibly be loaded with heavy metals, and drinking water, andin removing the heavy metals which are present in aqueous effluents (inparticular the polymers which possess the oxime functions), inparticular in a relatively wide pH range, and also in conditioningsludges.

[0016] In the treatment of waste water or drinking water, these polymerscan be employed either on their own or after using conventional ironand/or aluminum compounds.

[0017] When being used for treating waste water and drinking water,these novel polymers are generally effective in reducing the turbidityand the COD (chemical oxygen demand). Those possessing the oximefunctions (first part of the subject-matter of the invention) are able,in contrast to those possessing the amine functions, to decrease theresidual metal (aluminum, iron, etc.) content in the medium, when beingused for treating drinking water, and, furthermore, remove the heavymetals, when being used for treating waste water which contains thesemetals; when being used for treating sludges, the polymers possessingthe oxime functions are able, in contrast to those possessing the aminefunctions, to concentrate any possible heavy metals on the sludges to agreater extent.

[0018] Within the context of the invention, heavy metals are understood,in particular, as meaning metals having a valency greater than or equalto 2, preferably equal to 2, and, in particular, those selected fromantimony, arsenic, bismuth, cadmium, chromium, cobalt, copper, tin,manganese, mercury, molybdenum, nickel, gold, lead, thallium, tungsten,zinc, iron and the metals of the actinide family. The heavy metals whichare particularly aimed at are chromium, copper, nickel, iron, cadmium,mercury, lead and zinc. The heavy metals which are to be removed areusually present in the form of ions, in particular in the form of theirrespective cations.

[0019] The polymers which are used in accordance with a first part ofthe subject-matter of the invention are novel polymers which are derivedfrom polysaccharides which are formed from a main chain comprisingsimilar or different anhydrohexose units and branches comprising atleast one neutral or anionic anhydropentose and/or anhydrohexose unit.

[0020] These polymers can be obtained from polysaccharides which areavailable in substantial and renewable quantities. This is because thepolysaccharides which can be used for preparing the polymers accordingto the invention are derived from plants, such as cyanopsistetragonoloba, and carob seed. Furthermore, the polysaccharides areextracted very simply from these sources and do not require any specificchemical transformation.

[0021] It is to be noted that, according to the invention, the termcopolymeric polysaccharide signifies that the polymer is not selectedfrom those in which all the constituent units are identical. In thatwhich follows, and unless otherwise indicated, the term “polysaccharide”will be used instead of copolymeric polysaccharide.

[0022] The (similar or different) hexose units of the main chain of thenative skeleton of the polysaccharide can, in particular, be units whichare selected from D-glucose, D- or L-galactose, D-mannose, D- orL-fucose, L-rhamnose, etc.

[0023] The (similar or different) neutral or anionic pentose and/orhexose units of the branches of the native skeleton of thepolysaccharide can, more specifically, be units which are selected fromD-xylose, L- or D-arabinose, D-glucose, D- or L-galactose, D-mannose, D-or L-fucose, L-rhamnose, D-glucuronic acid, D-galacturonic acid andD-mannuronic acid, among others.

[0024] Furthermore, the polysaccharides from which the polymers used inthe invention are obtained can be used in the native state or else afterhaving undergone one or more depolymerization processes.

[0025] The galactomannans, the galactoglucomannans, the xyloglucans, thesuccinoglycans, the rhamsans and the welan gums, inter alia, may bementioned as examples of native polysaccharide skeletons.

[0026] The native skeleton of the polysaccharide from which the polymerused according to the invention is derived is preferably agalactomannan.

[0027] The galactomannans are macromolecules which are composed of amain chain of D-mannopyranose units, linked in the β(1-4) position,which is substituted by D-galactopyranose units in the α(1-6) position.

[0028] They are extracted from the albumen of leguminous seeds, of whichthey constitute the reserve carbohydrate. Preferred galactomannans whichmay be mentioned are guar gum, which is derived from guar seeds(Cyanopsis tetragonoloba), carob gum, with this being extracted from theseeds of the carob tree (Ceratonia siliqua), tara gum and cassia gum.

[0029] Quite preferably, the native skeleton is a guar gum. Morespecifically, the guar gums exhibit a mannose/galactose ratio of 2.

[0030] The weight average molar mass of the polysaccharides which can beused for obtaining the polymers used according to the invention can varyover a wide range. However, said polysaccharides advantageously exhibita weight average molar mass of between 10⁴ and 3.10⁶ g/mol (determinedby size exclusion chromatography).

[0031] The polysaccharides can be used in the form of a powder or ofparticles of a few millimeters in size. It is to be noted that, in thecase of galactomannans such as, in particular, guar, said particles aretermed splits and consist of the seed cotyledons, which have beenseparated from the central germ and the envelope. These splits can alsocontain water. The content of water depends to some degree on thehumidity of the ambient air. However, by way of illustration, thecontent of water is generally less than or equal to 10% by dry weight.

[0032] The polymers used in the invention therefore comprise one or moreunits which are carrying an oxime function at least in the C2 positionin the unit. The other positions in the unit, in addition to the carbonin the C2 position, which are capable of carrying such a function are,possibly, the C3 carbon atoms and, possibly, the C4 carbon atoms. It isto be noted that, depending on the nature of the unit and its positionin the polymer chain (main chain or branch), it may not be possible tooxidize the carbon in this position. In addition, it is pointed out thatthe polymers according to the invention may comprise units which do notcarry any oxime function. Furthermore, the polymer used can, whereappropriate, carry a carboxylic acid function (—COOH) in the C6 positionin one or more units.

[0033] When the polymer used according to the invention is composed ofdifferent types of oxidized carbon atoms (C2 and C3, C4 or C6), saidatoms may or may not be located in the same unit.

[0034] It is recalled that the C2 carbon is located in the α position tothe anomeric carbon.

[0035] According to one particularly advantageous embodiment of thepresent invention, the polymers are such that the majority (more than50% by number) of the oxime functions are carried by the carbon atoms inthe C2 position.

[0036] A preferred variant of the invention consists of the use of apolymer which is obtained from native or non-native (more specificallydepolymerized) guar and which carries an oxime function which is mainlyin the C2 position, with the majority of the substituted units beingthose which constitute the branches of the guar.

[0037] The first step in the process which can be used for preparing thepolymers used according to the invention will be described first of all.Step a) consists in bringing the native or non-native polysaccharideinto contact with an aqueous solution which comprises at least oneoxidizing agent which enables at least the hydroxyl radical carried bythe C2 carbon in one or more units to be oxidized to a ketone function.

[0038] A first embodiment of step a) consists in using thepolysaccharide in the form of an aqueous solution.

[0039] According to this embodiment, step a) is carried out in ahomogeneous phase.

[0040] A second embodiment of step a) consists in using thepolysaccharide in the form of a powder or of particles in the presenceof an organic compound which is selected from the solvents which do notdissolve the polysaccharide (nonsolvents). Under these conditions, thepreparation process is implemented in a heterogeneous form.

[0041] Said organic compound is selected from the compounds which areinert under the conditions of the reaction. Furthermore, said compoundsare preferably selected from the compounds which are at least partiallymiscible with water. Examples of these compounds which may be mentionedare, inter alia, hindered or unhindered alcohols, such as, veryparticularly, methanol, ethanol, isopropanol or tert-butanol; andketones, such as acetone.

[0042] Within the context of the second embodiment of step a), thereaction can be carried out in the presence of water. However, thequantity of water which is involved during this step is such that thepolysaccharide remains in the form of powder or particles which is/aredispersed in the reaction mixture. Thus, if step a) takes place in thepresence of water, the content of the latter preferably does not ingeneral exceed 30% by weight of the reaction mixture.

[0043] With regard to the nature of the oxidizing agent or the latter isadvantageously selected from bromine or the periodate of an alkali metalsuch as sodium. The oxidizing agent employed is preferably bromine.

[0044] It is to be noted that the oxidizing agent is used in the form ofan aqueous solution. The quantity of water supplied with the oxidizingagent is such that the reaction is still carried out in heterogeneousphase. Thus, the content of water supplied together with the oxidizingagent is preferably such that the maximum content of water in thereaction mixture is less than or equal to 30% by weight of the reactionmixture.

[0045] In certain cases, in particular that in which step a) is carriedout using periodate, it can be advantageous to recycle this oxidizingagent in the usual manner.

[0046] Furthermore, the molar ratio (oxidizing agent)/(functions to beoxidized) is more specifically less than 6, more particularly less than4 and preferably between 1 and 2.5.

[0047] According to one advantageous embodiment, step a) is carried outby adding the oxidizing agent to the polysaccharide.

[0048] In addition, a particularly appropriate variant of the inventionconsists in maintaining the pH during step a). The pH of the aqueoussolution is preferably maintained at a value between 6 and 8, veryadvantageously at a pH between 6.5 and 7.5.

[0049] The pH can be maintained by adding a base. It is to be noted thatthe base can either be added directly to the reaction mixture or addedto the solution of the oxidizing agent.

[0050] The temperature at which step a) is carried out is preferablybetween 0 and 70° C., advantageously between 10 and 30° C.

[0051] The skilled person can set the duration of step a) withoutdifficulty using standard analytical methods (¹³C NMR, infrared). As asimple illustration, and in the case of reaction conducteddiscontinuously and in homogeneous phase, the duration of step a) isless than 60 minutes, more specifically less than or equal to 30minutes, and preferably between 10 and 25 minutes. It is pointed outthat this length of time does not include that of introducing theoxidizing agent.

[0052] Attention is drawn to the fact that the polymer derived from stepa) can exhibit a carboxylic function on one or more of the repeatedunits of the initial polysaccharide. Such a function can be obtained byoxidizing the primary alcohol function if it is present in the unitunder consideration.

[0053] Furthermore, having been selectively oxidized during step a), theC2 carbon atom and, where appropriate, the C3 or C4 carbon atoms can bepresent in two different forms, with the one being in equilibrium withthe other. Thus, the ketone form can be present in equilibrium with thehydrated ketone form (^(HO)>C<^(OH))

[0054] At the conclusion of step a), which has just been described, theresulting polymer is such that it exhibits an average degree ofsubstitution of the secondary hydroxyl functions, more specificallycarried by the C2 carbon and, where appropriate, by the C3 or C4 carbonatoms, of between 0.01 and 2, preferably of between 0.1 and 1.

[0055] It is pointed out that the average degree of substitution iscalculated from carbon 13 NMR spectra and, more specifically, from theintegrals of the unresolved peaks which are characteristic of thefunctions which are present in the resulting polysaccharide.

[0056] Its value is given by the following calculation:${DS} = {\frac{\left( {I \times 100} \right)}{\left( {Ic}_{total} \right)} \times \frac{{DS}_{\max}}{\left( {100\quad C\quad \alpha \text{/}C\quad \beta} \right)}}$

[0057] in which:

[0058] I denotes the integral of the unresolved peak underconsideration;

[0059] Ic_(total) denotes the integral of all the unresolved peaks;

[0060] DS_(max) denotes the maximum degree of substitution; it is 2 inthe case of the ketone functions;

[0061] Cα denotes the number of carbons which can be modified perrepeated unit (example: galactose; mannose: Cα=4); and

[0062] Cβ denotes the average total number of carbons per repeated unit(example: galactose; mannose: Cβ=6).

[0063] At the conclusion of this step a), the resulting polymer ispreferably separated from the reaction medium.

[0064] When the reaction has taken place in homogeneous medium, theseparation can be effected by adding a nonsolvent of the resultingpolymer to the reaction medium. The nonsolvents mentioned within thecontext of the variant relating to the reaction in heterogeneous phaseare suitable and it is possible, therefore, to refer to them.

[0065] The polymer is then separated by filtration or centrifugation.

[0066] When the reaction is carried out in heterogeneous medium, thisseparation is effected by simple filtration or centrifugation.

[0067] As has previously been mentioned, step b) consists in bringingthe resulting polymer into contact with hydroxylamine, or a derivative,in order to transform the ketone function into an oxime function.

[0068] It is to be noted that, if a hydroxylamine derivative is used, itis selected from hydroxylamine sulfate and hydroxylamine chloride.

[0069] When step b) is carried out in the presence of a hydroxylaminederivative it is then preferable to carry out said step whilemaintaining the pH between 6 and 9.5. This can be effected, inparticular, by adding a base during the course of this step.

[0070] According to an advantageous embodiment of this step b), themolar ratio (hydroxylamine or derivative)/(ketone functions to betransformed) is between 1 and 10, preferably between 1 and 6.

[0071] In general, step b) is carried out using an aqueous solution ofthe hydroxylamine or hydroxylamine derivative.

[0072] Advantageously, the hydroxylamine or its derivative is employedin this step in the form of an aqueous solution in which theconcentration of the hydroxylamine or derivative is between 20 and 60%by weight.

[0073] The temperature at which step d) is carried out is morespecifically between 0 and 70° C., preferably between 10 and 30° C.

[0074] At the conclusion of this step b), the resulting polymer exhibitsan average degree of substitution of the ketone functions of less than2, preferably of between 0.01 and 2 excluded.

[0075] The average degree of substitution is once again determined fromcarbon 13 NMR spectra and, more specifically from the integrals of theunresolved peaks which are characteristic of the functions which arepresent in the resulting polysaccharide.

[0076] Its value is given by the following calculation:${DS} = {\frac{\left( {I \times 100} \right)}{\left( {IC}_{total} \right)} \times \frac{{DS}_{\max}}{\left( {100\quad C\quad \alpha \text{/}C\quad \beta} \right)}}$

[0077] in which:

[0078] I denotes the integral of the unresolved peak underconsideration;

[0079] IC_(total) denotes the integral of all the unresolved peeks;

[0080] DS_(max) denotes the maximum degree of transformation; it is 2 inthe case of the oxime functions;

[0081] Cα denotes the number of carbon atoms which can be modified perrepeated unit (example: galactose; mannose: Cα=4); and

[0082] Cβ denotes the average total number of carbons per repeated unit(example: galactose; mannose: Cβ=6).

[0083] Once again, it can be preferable to separate the resultingpolymer from the reaction medium. This procedure can, in particular,take place in the same way as in the case of step a).

[0084] The present invention also relates to the use, for the treatmentof aqueous media or for sludge conditioning, of a novel polymer which isderived from a polysaccharide which is formed from a main chaincomprising similar or different anhydrohexose units and from branchescomprising at least one neutral or anionic anhydropentose and/oranhydrohexose unit, with said polymer comprising one or more units whichcarry an amine function at least in the C2 position and being capable ofbeing obtained by implementing a step c) which consists in bringing thepolymer possessing one or more units carrying an oxime function at leastin the C2 position into contact with an agent which reduces the oximefunction.

[0085] The polymers thus used according to the invention thereforecomprise one or more units which carry an amine function in the C2position in the unit, and, where appropriate, on the C3 carbon atomsand, where appropriate, on the C4 carbon atoms. In addition, it ispointed out that said polymers can comprise units which do not carry anyoxime function. Furthermore, these polymers can, where appropriate,carry a carboxylic acid function (—COOH) in the C6 position in one ormore units.

[0086] Finally, when the polymer used according to the inventioncomprises different types of carbon atom carrying an oxime function (C2and C3 or C4), said atoms may or may not be located in the same unit.

[0087] The reaction which is brought into play for obtaining the polymercomprising one or more amine functions can take place by using, as theagent for reducing the oxime function to an amine function, an agentwhich is selected from lithium hydride and aluminum hydride; and boroncompounds such as BH₃, NaBH₄, NaBH₃CN and NaBH₂S₃, which may or may notbe combined with a Lewis acid. Lewis acids which can be used, preferablyin combination with borohydride or cyanoborohydride, and which may bementioned are molybdenum oxide, nickel chloride, titanium chloride andtitanium oxide.

[0088] This type of agent is customarily, and advantageously, used inthe presence of water, with the exception of lithium aluminum hydridewhich is preferably used in the presence of a solvent of thetetrahydrofuran type.

[0089] The temperature can vary over a wide range. As an indication, itis between 10° C. and the temperature at which the medium refluxes.

[0090] It is also possible to use hydrogen in the presence of a catalystof the palladium on carbon type, where appropriate in the presence ofhydrochloric acid, or of the platinum oxide type or Raney nickel type.

[0091] The pH at which the reaction is carried out can vary over arelatively extended range, depending on the nature of the reducing agentwhich is selected. Thus, as an example, and in the specific case of areduction carried out using a borohydride, the pH is advantageouslybetween 3 and 10.

[0092] Finally, this step c) is preferably carried out under an inertatmosphere. Thus, nitrogen or rare gases can be used in the appropriatemanner.

[0093] In general, the quantities of novel polymers employed inaccordance with the invention correspond to those used in the case ofthe products which are customarily employed in the treatments concerned.

[0094] Examples which are specific, but which do not limit theinvention, will now be presented.

EXAMPLES

[0095] In the examples which follow:

[0096] 1/the weight average molar masses of the polymers carrying ketoneor oxime functions are determined as follows:

[0097] The measurement is carried out in: Millipore 18 MΩ water, 30%MeOH, 0.1 M LiCl, pH 9-10 (2/10000 parts of NH₄OH).

[0098] The features of the equipment are as follows:

[0099] Chromatographic columns: 1 Shodex SB806HQ 30 cm, 5 μm column+1Asahi GFA30 60 cm, 5 μm column.

[0100] Injection pump: Wisp 717+Waters 515 pump

[0101] Detector: Waters 410 RI refractometer, sensitivity 8, Wyatt MALLSlight scattering, He 633 nm laser

[0102] Flow rate: 0.5 ml/mn

[0103] The injected solution (200 μl) contains {fraction (1/1000)} byweight of polysaccharide.

[0104] The weight average molecular mass is established directly withoutcalibration using the light scattering values extrapolated to zeroangle; these values are proportional to C×M×(dn/dc)2.

[0105] C corresponds to the concentration of polysaccharide

[0106] M corresponds to the weight average molecular mass

[0107] n corresponds to the refractive index of the solution

[0108] c corresponds to the concentration of polysaccharide

[0109] the ratio dn/dc is in this present case equal to 0.15.

[0110] 2/nitrogen is determined using a Carlo Erba EA1108 analyzer,which analyzes C, H, N and S simultaneously in organic substances usingthe classical methods of Dumas and Pregl.

[0111] The analyzer comprises 2 essential parts having very distinctfunctions:

[0112] 1. A reactor, which consists of a quartz column having tieredfilling. This is the site of the successive transformations of thesamples (combustion, oxidation and reduction) in order to extract thesought-after elements C, H, N and S in the form N₂, CO₂, H₂O and SO₂.

[0113] 2. An analytical cell, which consists of a gas chromatographycolumn and catharometric detection.

[0114] The processing of the data is managed entirely by a microcomputerwhich is equipped with the Eager 200 software supplied by themanufacturer Carlo Erba.

[0115] With the content of nitrogen being expressed in percentage byweight, the amine function DS is calculated using the following formula:

DS=162.Y/(1400+15Y), where Y is the percentage of nitrogen by weight.

[0116] This formula is obtained bearing in mind that the polymer has thefollowing empirical formula:

C₆H_((10+DS))O_((5−DS))N_((DS))

Example 1 Synthesizing a Polymer which is Derived from Guar and CarriesKetone Functions

[0117] 54 grams of guar (weight average molar mass: 50000g/mol—Meyprogat® 7, marketed by Rhodia) are dissolved in 840 ml ofwater.

[0118] In addition, a solution of bromine is prepared by adding 26 ml ofbromine to 250 ml of water and then neutralizing by adding sodiumhydroxide solution (2N) in order to obtain a stable pH of 7.6.

[0119] The bromine solution which is thus obtained (2 equivalents peranhydropyrannose motif) is then added dropwise to the polymer.

[0120] While the bromine is being added, and until the pH no longerchanges, sodium hydroxide solution (2N) is added so as to maintain thepH at approximately 7.

[0121] When the pH has stabilized, the reaction mixture is poured intoethanol so as to precipitate the polymer which has been obtained. Thepolymer is then filtered on a no. 4 frit.

[0122] At the conclusion of this step, the polymer possesses ketonefunctions predominantly at positions C2 and C3.

[0123] For the analysis, the product is dried by lyophilization.

[0124] The ¹³C NMR spectrum is analyzed.

[0125] Conditions: 400 MHz

[0126] Solvent: D₂O

[0127] Temperature 70° C.

[0128] Accumulation time: approximately 48 hours.

[0129] Results:

[0130] Comparison of the spectrum of the starting polymer and of thatderived from the reaction shows the appearance of three new unresolvedpeaks which are characteristic of the ketone, hydrated ketone andcarboxylic acid functions.

[0131] In addition, the degree of ketone substitution, as calculatedfrom the 13C NMR spectrum, is 0.53.

[0132] The weight average molar mass is 6500 g/mol.

Example 2 Synthesizing the Polymer Comprising the Oxime Functions

[0133] 40 g of the product in the solid and dry state, as previouslyobtained, are dissolved in 700 ml of water. The pH of the solution isapproximately 7.

[0134]76 ml of a 50% by weight solution of hydroxylamine in water areadded to the solution.

[0135] After addition, the pH is 9.4.

[0136] The whole is left to stir for 18 hours. The pH is 9.1.

[0137] At the conclusion of this step, the product is separated off byprecipitation in ethanol and filtration on a no. 4 frit.

[0138] For the analysis, the product is dried by lyophilization.

[0139] Comparison of the ¹³C NMR spectra (ambient temperature, 4 hours)of the polymers obtained during the oxidation step and after theoximation step shows the appearance of an unresolved peak which ischaracteristic of the oxime function.

[0140] Elemental analysis of the polymer (determining the nitrogen bythermally degrading the compound and then using gas chromatography toanalyze the emitted gases) indicates that the transformation of theketone functions is almost quantitative.

[0141] The calculated degree of substitution is 0.46.

[0142] The weight average molar mass is 5100 g/mol.

Example 3 Synthesizing the Amine Derivative

[0143] 8 ml of a 13% solution of TiCl₃ in 20% HCl, and 10 ml of water,are initially introduced into a stirred glass reactor.

[0144] 2 g of NaOH which has been previously dissolved in 10 ml of waterare then added. A violet precipitate is then formed.

[0145] 10 ml of an aqueous solution containing 500 mg of NaBH₄ are thenadded to this mixture and, after stirring for 15 minutes, 1 g of guaroxime from the previous example, dissolved in 15 ml of water, isintroduced.

[0146] The medium becomes white and very viscous; it is left to stirunder nitrogen for 48 hours.

[0147] At the end of this period, the pH of the medium is 8.5.

[0148] The solid phase of the reaction medium is separated from theliquid phase by filtration and the modified guar, which is located inthe liquid, is recovered by means of precipitation in a nonsolvent(ethanol) and filtration.

[0149] The polymer is analyzed by ¹³C NMR.

[0150] Under these conditions, it is seen that the unresolved peak ofthe oxime at 154 ppm has disappeared.

[0151] In parallel, peaks appear at about 54 ppm, corresponding tocarbon atoms which are carrying an amine function.

[0152] The ¹H NMR confirms this result since there are characteristicsignals of the proton in the α position of an amine function between 1and 2.5 ppm.

[0153] Finally, elemental analysis enables the nitrogen content to bemeasured. It is 4.1 as compared with 4.2 in the case of the oximatedproduct.

Example 4

[0154] The polymer obtained at the end of example 2, and also a cationicpolyacrylamide marketed by the company SN FLOERGER under referenceF04698, are subjected to a synthetic waste water clarification test.

[0155] a—Synthesis of the Waste Water:

[0156] The following are mixed in a 1 liter container: demineralizedwater 0.5 l bentonite (clay) 3.2 g ± 0.1 g sugar 2.4 g ± 0.1 g humicacid (Na) 0.2 g ± 0.1 g CaCl₂ 5.1 g ± 0.1 g NH₄Cl 4.0 g ± 0.1 g K₂HPO₄2.0 g ± 0.1 g NaHCO₃ 8.0 g ± 0.1 g Na₂S, 9H₂O 308 mg ± 5 mg 

[0157] The mixture is then homogenized for 15 minutes using anultrasonicator.

[0158] The suspension volume is made up to 1 liter using demineralizedwater.

[0159] The suspension is transferred into a 30 liter polyethylene tank.

[0160] 4 liters of demineralized water are added using a 1 litercontainer, with this being followed by 3 cans, each of which contains 5liters of demineralized water. Calcium-rich powdered milk (7.7 g±0.1 g)is then added to the suspension.

[0161] Finally, the latter is stirred for from 1.5 to 2 hours using amechanical stirrer (300 rpm) fitted with a paddle having two retractablearms.

[0162] b—Clarification Test

[0163] A KEMIRA 208 flocculator, whose thermostated bath is set to atemperature of 17° C., is used.

[0164] The stirring times are regulated in accordance with the sequenceof programmed operations in 6 different pots: 1 2 3 4 5 6 Rapid 60 s 60s 60 s 60 s 60 s 60 s stirring Slow stirring 10 10 10 10 10 10 min minmin min min min Sedimentation 15 15 15 15 15 15 min min min min min min

[0165] In order to determine the product dose which leads to the optimumpurification performance of said product, 1000 ml of synthetic wastewater, to which the product has been added at 6 different doses, areintroduced into the 6 pots.

[0166] The 6 stirrers are placed in the pots.

[0167] Each programmed operation is started consecutively about every 2minutes.

[0168] Each stirrer is withdrawn as soon as the sedimentation begins inthe corresponding pot.

[0169] At the end of the sedimentation, a siliconated polyethylene tubefilled with water is used to aspirate 100 ml of clarified water in orderto rinse said tube.

[0170] While keeping one of the ends of the tube in the supernatantsolution, a sample of 250 ml of clarified water is then withdrawn.

[0171] 0.04 mg of cationic polyacrylamide F04698, dissolved in water atthe rate of 1 g/liter, is used per liter of waste water to be treated.

[0172] At the end of the treatment, a percentage reduction in theturbidity of 97.1% and a percentage reduction in the COD of 41.8% areobtained.

[0173] 0.05 mg of the polymer obtained at the end of example 2,dissolved in water at the rate of 1 g/liter, is used per liter of wastewater to be treated.

[0174] At the end of the treatment, a percentage reduction in theturbidity of 98.6% and a percentage reduction in the COD of 50.1%, andtherefore percentage reductions, particularly in regard to the COD,which are definitely greater than those obtained with the controlF04698, are obtained.

1-26 (Canceled)
 27. A process for the treatment of aqueous media or forsludge conditioning, comprising the step of treating said aqueous mediaor sludge with of at least one polymer derived from a copolymericpolysaccharide formed from a main chain comprising similar or differentanhydrohexose units and branches which comprise at least one neutral oranionic anhydropentose and/or anhydrohexose unit; said derived polymercomprising one or more units which carry(ies) an oxime function at leastin the C2 position and being capable of being obtained by implementingthe following steps: a) bringing a polysaccharide into contact with anaqueous solution which comprises at least one oxidizing agent whichenables at least the hydroxyl radical carried by the C2 carbon of one ormore units to be oxidized to a ketone function; and b) bringing theresulting polymer into contact with hydroxylamine, or a derivative, inorder to transform the ketone function into an oxime function.
 28. Theprocess as claimed in claim 27, wherein the oxime function is located onthe C2 carbon of the unit, on the C3 carbon, or on the C4 carbon. 29.The process as claimed in claim 27, wherein one or more of the unitscarry(ies) a carboxylic acid function (—COOH) on the carbon atom inposition C6.
 30. The process as claimed in claim 29, wherein thepolysaccharide is a galactomannan.
 31. The process as claimed in claim30, wherein the galactomannan is guar, carob, tara or cassia gums. 32.The process as claimed in claim 27, wherein the polysaccharide is in theform of an aqueous solution.
 33. The process as claimed in claim 32,wherein step a) is performed in homogeneous phase.
 34. The process asclaimed in claim 27, wherein the polysaccharide is in the form of apowder or particles.
 35. The process as claimed in claim 34, whereinstep a) is performed in heterogeneous phase.
 36. The process as claimedin claim 27, wherein the oxidizing agent is a bromine or a periodate ofan alkali metal.
 37. The process as claimed in claim 27, wherein theoxidizing agent has a molar ratio relative to the functions to beoxidized, of less than
 6. 38. The process as claimed in claim 37,wherein the molar ratio is between 1 and 2.5.
 39. The process as claimedin claim 27, wherein step a) is performed by adding the oxidizing agentto the polysaccharide.
 40. The process as claimed in claim 27, whereinstep a) is performed while maintaining the pH of the aqueous solution ata value which is between 6 and
 8. 41. The process as claimed in claim27, wherein the pH is maintained at between 6 and 9.5 during step b).42. The process as claimed in claim 27, wherein step b) is implementedin the presence of a molar ratio of hydroxylamine or derivative relativeto the ketone functions present, of between 1 and
 10. 43. The process asclaimed in claim 27, wherein step b) is implemented using an aqueoussolution of hydroxylamine or derivative.
 44. The process as claimed inclaim 27, wherein the polymer resulting from step a) or the polymerresulting from step b) is further separated from the reaction medium bybeing precipitated in a non-solvent of the polymer.
 45. The process forthe treatment of aqueous media or for sludge conditioning, of at leastone polymer derived from a copolymeric polysaccharide formed from a mainchain which comprises similar or different anhydrohexose units andbranches which comprise at least one neutral or anionic anhydropentoseand/or anhydrohexose unit, said polymer comprising one or more unitswhich carry(ies) an amine function at least in the C2 position and beingcapable of being obtained by implementing step c) consisting in bringingthe polymer possessing one or more units carrying an oxime function atleast in the C2 position, as defined in claim 27, into contact with anagent which reduces the oxime function.
 46. The process as claimed inclaim 45, wherein the amine function is located on the C2 carbon of theunit, on the C3 carbon, or on the C4 carbon.
 47. The process as claimedin claim 45, wherein one or more of the units carry(ies) a carboxylicacid function (—COOH) on the carbon atom in the C6 position.
 48. Theprocess as claimed in claim 45, wherein step c) is implemented in thepresence of lithium aluminum hydride or of boron compounds, optionallycombined with a Lewis acid which is molybdenum oxide, nickel chloride,titanium chloride or titanium oxide.
 49. The process as claimed in claim45, wherein step c) is implemented at a pH of between 3 and
 10. 50. Theprocess as claimed in claim 45, wherein step c) is implemented under aninert atmosphere.
 51. The process as claimed in claim 27, wherein theaqueous effluents contain heavy metals.
 52. The process as claimed inclaim 45, wherein the aqueous effluents contain heavy metals.
 53. Theprocess as claimed in claim 27, wherein the aqueous media are wastewater.
 54. The process as claimed in claim 27, wherein the aqueous mediaare drinking water.